Method and system for communication spectral backward compatibility

ABSTRACT

Communications method including the procedures of modulating a second generation carrier signal, with a first generation Baseband bandwidth signal, when transmitting to first generation devices, and, modulating the second generation carrier signal, with a second generation Baseband bandwidth signal, when transmitting to second generation devices, wherein the first generation Baseband bandwidth signal, is shaped so as to recreate a first generation signal, when up-sampled and modulated with a second generation carrier signal.

REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.10/119,421 filed Apr. 9, 2002 (pending), which is a continuation-in-partof U.S. patent application Ser. No. 10/055,197 filed Jan. 21, 2002(pending), both of which are hereby incorporated by reference in theirentireties.

FIELD OF THE TECHNOLOGY

The disclosed technique relates to communication methods and systems, ingeneral, and to methods and systems which are backward compatible withprior generations thereof, in particular.

BACKGROUND OF THE DISCLOSED TECHNIQUE

Networked devices communicate using signals sent over common physicalmedia networks, which can be either wired or wireless. Such a networkinterconnects devices of different generations having differentcommunication parameters. Backward compatibility of new generationdevices with older generation devices, is a desired quality.Compatibility implies co-existence, such that new generation devices donot interfere with old generation transmissions. Compatibility mayfurther imply interoperability, such that new generation devices and oldgeneration devices, are able to communicate there between.

Such devices may be connected in a point-to-point architecture, whereinonly two such devices are connected, or in a networked architecture,wherein a plurality of devices share the same physical communicationmedium and intercommunicate there between.

Conventional communication standards employ several methods in order toensure backward compatibility. One type of such methods is called“Fall-back”. “Fall-back” methods artificially degrade the capabilitiesof the later generation device, forcing them to be comparable with thoseof prior generation devices. A network which is composed of both priorand later generation devices, operates according to the communicationstandard of the prior generation devices, even for communication betweentwo later generation devices.

Another type of such methods is called self-describing frame formatmethods. In these methods, when two later generation devicescommunicate, later generation data formatted transmission isencapsulated, such that the header of the transmission is in priorgeneration format. The header can include information related to thegeneration of the data encapsulated thereafter or information related toa destination node. A prior generation device, receiving such data,after decoding the header portion of the data, shall determine that thisdata is not intended therefor and hence shall ignore the rest of thedata. A later generation device, receiving the same transmission, afterdecoding the header, will decode the rest of the data, using the newercommunication standards.

A further method of providing backwards compatibility, is by adding acomponent, to each prior generation device, which will providetranslation capabilities, of later generation standards, to thoserecognizable by the prior generation device, and vice versa. Suchdevices allow communication across the network to be conducted, usinglater generation technology, while allowing prior generation devices, toparticipate in the data exchange across the network.

U.S. Pat. No. 6,298,051, entitled “High-data-rate supplemental channelfor CDMA telecommunications system”, issued to Odenwalder et al., isdirected to a method for transmitting a supplemental high rate datachannel in tandem with existing data channels over a CDMA over-the-airtransmission. This is accomplished by providing a quadrature-phasechannel, orthogonal to the in-phase channels used to transmitnormal-rate CDMA data, in such a way as to avoid interfering with thein-phase channel. Thus, normal rate capable CDMA devices, which areunable to detect the quadrature-phase channel, are not influenced by thehigh rate data. The method thus illustrated ensures compatibility of thehigh-rate capable devices with the normal rate devices.

U.S. Pat. No. 6,011,807, entitled “Method and apparatus for transmittingdata in a high rate, multiplexed data communication system”, issued toCastagna et al., is directed to a method and apparatus for determiningsynchronization and loss of synchronization in a high rate multiplexeddata system. The method employs a backwards compatibility flag thatallows the apparatus to operate with older systems. By using thebackwards compatibility flag to detect if an incoming transmission isinitiated in an older system, and activating relevant circuitryaccordingly, the apparatus is able to maintain compatibility with oldersystems.

U.S. Pat. No. 5,987,068, entitled “Method and apparatus for enhancedcommunication capability while maintaining standard channel modulationcompatibility”, issued to Cassia et al., is directed to a method forenhancing communication capabilities. The method modulates a firstcommunication signal, using a standard modulation technique, onto acarrier signal, thereby producing a first transmission signal. Themethod further modulates a supplemental communication signal onto thefirst transmission signal, thereby producing a combined transmissionsignal, which is then broadcast. The standard modulation scheme for thefirst communication signal, is differential quadrature phase shiftkeying (DQPSK). When the combined transmission signal is demodulatedusing DQPSK, the first communication signal is extracted there from.When a receiving device is aware of the enhanced modulation scheme usedin the combined transmission signal, it demodulates the signalaccordingly, extracting both the first communication signal, and thesupplemental communication signal. When a receiving device is not awareof the enhanced modulation scheme it demodulated the combinedtransmission signal using DQPSK demodulation, extracting the firstcommunication signal. Thus compatibility is ensured when transmitting toa device unaware of the enhanced modulation scheme used.

IEEE Standard 802.3 details the standards for the Ethernet localnetworking interface and protocol. The 802.3 standard encompassestechnologies of various communication rates, namely 10 Mbps, 100 Mbpsand 1000 Mbps. In order to ensure backwards compatibility between newerhigh-rate devices and older low-rate devices, the standard details anauto-negotiation implementation. Accordingly, high-rate devices detect atransmission from a low-rate device, infer a connection to such adevice, and reduce the communication rate accordingly. Such a ratereduction ensures backward compatibility with the low-rate communicationdevice.

A family of communication specifications which exhibit backwardcompatibility, is known as Home Phoneline Networking Alliance (HPNA).The first generation, HPNA-1, defines transmission around a carrierfrequency F_(HPNA-1), with Pulse Position Modulation.

The second generation defines transmission around a carrier frequencyF_(HPNA-2), but with Frequency Diverse/Quadrature Amplitude Modulation(FDQAM/QAM). An HPNA-2 device which communicates with an HPNA-1 device,transmits an HPNA-1 format pulsed transmission around F_(HPNA-1) usingan HPNA-1 transmitter incorporated into the HPNA-2 device. In thepresence of HPNA-1 devices, an HPNA-2 device which communicates with anon-HPNA-1 device, commences a transmission with an HPNA-1 format pulsedlike header, encapsulating information which causes HPNA-1 devices todiscard the rest of the transmission.

U.S. patent application Ser. No. 2002/0015404, entitled “ExtendedBandwidth HomePNA System Compatible with HomePNA 2.0”, by Fisher et al.,is directed to a method for using an extended bandwidth HPNA system,compatible with the HPNA 2.0 standard, in such a way as to cause HPNA2.0 systems to ignore transmissions not intended for those systems. Thesystem uses a transmission signal centered on 10 MHz, having a 12 MHzbandwidth, to communicate between extended bandwidth systems. In orderto allow for compatibility with HPNA 2.0 systems, the proposed systemproduces a training sequence that an HPNA 2.0 system is able to train onand determine that the incoming packet is not intended for the HPNA 2.0receiver. The training sequence is produced by zero padding a 2 MBaudsymbol sequence to an 8 MBaud sequence (up-sampling the signal), andthen modulating the 8 MBaud sequence on to a 1 MHz carrier. Thismodulation shift the spectrum of the 8 MBaud sequence by 1 MHz. Theshifted signal is then modulated on the 10 MHz carrier. The portion ofthe modulated signal between 4 MHz and 10 MHz is identical to an HPNA2.0 signal, thus allowing an HPNA 2.0 receiver to train on the trainingsequence.

SUMMARY OF THE DISCLOSED TECHNIQUE

It is an object of the disclosed technique to provide a novel method andsystem for backward compatibility between different generations ofcommunication devices, interconnected on the same physical network.

In accordance with the disclosed technique, there is thus provided amethod to ensure backward compatibility between different generations ofcommunication devices. The method includes the procedure of mixing afirst generation bandwidth Baseband signal, to produce a mixed firstgeneration Baseband signal, having a first generation Basebandbandwidth, when transmitting to first generation devices, by secondgeneration devices, the mixing is performed such that the mixed firstgeneration Baseband signal, is spectrally shifted with respect to saidfirst generation Baseband signal, by a factor equal to the fractionportion of the difference between a first generation carrier signalfrequency and a second generation carrier signal frequency, divided bysaid first generation Baseband bandwidth. The method further includesthe procedure of modulating the mixed signal with a second generationcarrier signal. The modulation creates at least one copy of the Basebandsignal, centered on an old generation carrier frequency, thus, oldgeneration devices, can demodulate the Baseband signal, therebyreceiving data from new generation devices.

In accordance with another aspect of the disclosed technique, there isthus provided a second generation communication device which cantransmit backward compatible signals, to first generation devices. Thedevice includes a first signal generator, generating a first generationbandwidth Baseband signal, a second signal generator, generating asecond generation bandwidth Baseband signal, a signal shaper, anup-sampler, a controller, a switch, a carrier signal generator, and amodulator. The signal shaper is coupled with the up-sampler and thefirst signal generator. The switch is coupled with the up-sampler, thesecond signal generator, the controller and the modulator. The modulatoris coupled with the switch, the carrier signal generator and thecommunication interface. When data is transmitted to new generationdevices, the controller selects the second signal generator, whichprovides a second generation Baseband signal to the modulator, via theswitch. The modulator modulates a carrier signal provided by the carriersignal generator, with second generation Baseband signal, therebycreating a transmission signal. The communication interface transmitsthe transmission signal to the network. When data is transmitted to oldgeneration devices, the controller selects the first signal generator,which provides a first generation Baseband signal to the signal shaper.The signal shaper shapes the first generation bandwidth Baseband signal,to produce a first generation basic signal copy, when duplicated in thefrequency domain, and centered on a second generation carrier signal,and provides the shaped signal to the up-sampler. The up-samplerup-samples the shaped Baseband signal. The up-sampled signal is providedto the modulator via the switch. The modulator modulates the carriersignal with the up-sampled Baseband signal, thereby creating atransmission signal. The communication interface transmits thetransmission signal to the network.

In accordance with another aspect of the disclosed technique, there isthus provided a method to ensure coexistence between differentgenerations of communication devices sharing the same physical network.The method includes the procedure of prepending a second generationtransmission signal, with a shaped first generation header, thuscreating a pre-modulated transmission signal, the shaped header, shapedsuch that a first generation header is recreated when modulated with asecond generation carrier signal. The header instructs first generationdevices to ignore the rest of the transmitted signal. The method furtherincludes the step of modulating the pre-modulated transmission signalwith a second generation carrier signal and transmitting the producedsignal to the network. Thus, when first generation devices receive thetransmitted signal the header will instruct them to ignore the rest ofthe signal, insuring coexistence with second generation devices.

In accordance with another aspect of the disclosed technique, there isthus provided a second generation communication device which can coexistwith first generation devices, sharing the same physical network. Thedevice includes a signal generator, generating a second generationBaseband signal, a memory element, a controller, a switch, a carriersignal generator, a modulator and a communication interface. The switchis coupled with the memory element, the signal generator, the controllerand the modulator. The modulator is further coupled with the carriersignal generator and the communication interface. The memory elementcontains a shaped copy of a first generation format Baseband signal,shaped so as to recreate said first generation format Baseband signalwhen modulated with said second generation carrier signal anddemodulated with respect to a first generation carrier signal. Theshaped copy of a first generation format Baseband signal is at least aportion of a first generation format header instructing first generationdevices to ignore the rest of the transmitted data. The switch prependsthe shaped copy of a first generation format Baseband signal, retrievedfrom the memory element, to the signal received from the signalgenerator, and provides the combined signal to the modulator. Themodulator modulates the combined signal, with a second generationcarrier signal, provided from the carrier signal generator, andtransmits the signal to the network, via the communication interface.Thus, first generation devices receiving the signal will decipher theheader and ignore the rest of the signal, allowing for coexistence onthe same network.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosed technique will be understood and appreciated more fullyfrom the following detailed description taken in conjunction with thedrawings in which:

FIG. 1A is a schematic illustration, in the frequency domain, of atransmission signal, which is produced by modulating an up-sampleddiscrete Baseband signal onto a continuous carrier signal;

FIG. 1B is a schematic illustration, in the frequency domain, of anoriginal signal and a shaped signal, which is produced by spectrallyshaping the original signal;

FIG. 2 is a schematic illustration, in the frequency domain, of threetransmission signals, some of which are defined and produced inaccordance with an embodiment of the disclosed technique;

FIG. 3 is a schematic illustration, in the frequency domain, of threetransmission signals, some of which are defined and produced inaccordance with another embodiment of the disclosed technique;

FIG. 4 is a schematic illustration, in the frequency domain, of anHPNA-2 mode of operation transmission signal and two additionaltransmission signals defined and produced in accordance with a furtherembodiment of the disclosed technique;

FIG. 5 is a schematic illustration of a network, which includescommunication devices from different generations;

FIG. 6A is a schematic illustration of a new generation devicetransmitter, constructed and operative in accordance with an embodimentof the disclosed technique; and

FIG. 6B is a schematic illustration of a new generation devicetransmitter, constructed and operative in accordance with an embodimentof the disclosed technique; and

FIG. 7A is a schematic illustration of a new generation devicetransmitter, constructed and operative in accordance with an embodimentof the disclosed technique;

FIG. 7B is a schematic illustration of a new generation devicetransmitter, constructed and operative in accordance with an embodimentof the disclosed technique; and

FIG. 8 is a schematic illustration of a method for backward compatiblecommunication, operative in accordance with another embodiment of thedisclosed technique.

DETAILED DESCRIPTION OF EMBODIMENTS

The disclosed technique overcomes the disadvantages of the prior art byproviding a novel method for communication backward compatibility, whichtransmits at old generation transmission rate, centered on a newgeneration carrier frequency. The disclosed technique can be implementedfor both analog and digital transmissions.

The terms “old generation” and “new generation” merely represent twodifferent communications specifications, which do not necessarily differin the point in time, in which each was defined, and hence, for example,can be two communications specifications which were defined at the sametime for different purposes. The terms “new” and “old” areinterchangeable. Moreover, the two generations can be different modes ofoperation within the same communications specification. Similarly, suchtwo generations, can be two separate communications specification thatbelong to different methodologies which belong to different families ofmethodologies. The disclosed technique can be applied to any twocommunications specifications, which comply with basic requirements,such as outlined herein below.

In the following description the following terms are used:

-   -   Data signal—A signal which can be analog or digital, which can        be presented at different levels of encoding, such as raw (i.e.,        not encoded), encapsulated in data packets (which may include        additional information such as headers, error detection and        correction sections, and the like), encryption, compression, and        the like.    -   Baseband signal—An original band of frequencies produced by a        signal generating device, which can be analog or digital. A        Baseband signal is usually used to modulate a carrier signal        thereby producing a transmission signal. Demodulation of the        transmission signal by the carrier signal, re-creates the        Baseband signal. Baseband frequencies are usually characterized        by being lower in frequency than the frequencies of the        transmission signals, and in some cases also lower than the        frequencies of carrier signals or sub-carrier signals. The        sampling frequency of the Baseband defines a Baseband bandwidth,        which is essentially equal thereto. The Baseband bandwidth is        the difference between the highest, and lowest, frequency        components in the transmitted Baseband signal. It is noted that        the sampling frequency of a digital format Baseband signal is        also known as baud-rate.    -   Frequency range—The frequency range is the continuous range of        frequencies used for the transmission of the signal. The        difference between the highest, and lowest frequency in the        frequency range, is the bandwidth of the signal.    -   Carrier signal—A cyclic signal which can be analog or digital,        at a frequency which in most cases is higher than that of        Baseband signals. It is noted that in conventional communication        standards, a carrier signal is characterized by a fixed        predetermined frequency, although a communication standard may        define a plurality of carrier signals, each at a different        frequency. A single carrier signal can be described as        S(t)=Ae^(i2πf) ^(c) ^(t), wherein f_(c) denotes the carrier        frequency. Transmission signal—A signal which is physically        transmitted across a physical medium, either wired or wireless.        The transmission signal is produced by modulating the carrier        signal with the Baseband signal. The transmitted signal        typically centers on the carrier signal and spreads at least        across a range of frequencies, which can be finite or infinite.    -   Delta function—A single infinite peak, which exists only at a        predetermined point, in a given domain. The fundamental property        of a delta function is that the integration of the product of a        delta function, and a signal function, over the entire domain,        equals the value of the signal function, at the point where the        delta function is infinite.    -   Delta function array—A series of delta functions, spaced apart        at a predetermined interval, in a given domain.    -   Fourier transform—A mathematical transformation of a function,        from one domain to another. The transformed function can be        discrete (e.g., a delta function, a plurality of delta        functions, and the like) or continuous (e.g., a SIN function,        and the like) as is the result of the transformation. In the        following description, Fourier transforms are performed between        the time domain and the frequency domain.    -   Up-sampling—increasing the sample rate of a digital signal by        inserting additional samples in a stream of original samples, at        predetermined locations therein. The most common case of        up-sampling is the insertion of zero value samples between        original samples. This type of up-sampling produces exact        spectral copies of the original signal in the frequency domain.    -   Signal shaping—a process by which a desired spectral shape is        imposed on a data signal, by using a shaping function.    -   Mixing—a process by which two data signals are multiplied,        creating a new output signal. It is noted that one of the        signals may be selected to be a shaping function signal, which        is directed at imposing a desired change on the data signal, so        that the output signal is an accordingly changed copy of the        data signal. For example, the shaping function signal may be        selected so that the desired change is a phase shift, an        amplitude adjustment, and the like. Mixing is one example of a        signal shaping technique.    -   Modulation—a process by which an arbitrary signal is mixed with        a cyclic signal, producing a combined signal. The combined        signal is then filtered to occupy a specified bandwidth and the        resulting filtered signal is the product of the modulation.

A digital Baseband signal is a series of values, each at a certain pointin time and hence, the digital Baseband signal can be represented as aseries of delta functions in the time domain, spaced apart at apredetermined interval. The Baseband signal modulates the carriersignal, thereby producing the transmission signal. Extracting the datasignal from a received transmission signal requires demodulation of thecarrier signal, to obtain the Baseband signal.

It will be appreciated by those skilled in the art that a product of theBaseband signal and the carrier signal, in the time domain is equivalentto the convolution of the Fourier transform of the two signals.δ(t)·f(t)

F(ω)*Δ(ω)

It is noted that a Fourier transform of a delta function array in onedomain, is also a delta function array, with a different interval inanother domain.

In addition, when a delta function array signal is modulated on acontinuous signal, the product signal is equal to a convolution of thetwo in the frequency domain. The product signal, when represented in thefrequency domain, contains a plurality of copies of a basic signal.

When the continuous signal exhibits a single frequency, each copy of thebasic signal is centered on a different frequency, one of them beingthat of the continuous signal. The center frequencies are spacedaccording to the interval bandwidth of the delta function array signal.

Multiple copies of a digital format Baseband signal may be created byup-sampling the Baseband signal. Digital up-sampling may be viewed inthe frequency domain, as broadening the digital frequency range, whilekeeping the same analog spectrum. Therefore, more spectral copies willbe included in the digital frequency range. It will be appreciated thatup-sampling may be performed either before, or after a transmissionsignal has been modulated with a carrier signal, by employingessentially the same techniques.

Reference is now made to FIG. 1, which is a schematic illustration, inthe frequency domain, of a transmission signal, generally referenced 10,which is produced by modulating a Baseband signal onto a carrier signal.

Transmission signal 10 includes a basic signal 140 and a plurality ofbasic signal copies 14 ⁻², 14 ⁻¹, 14 ₊₁ and 14 ₊₂ thereof. Basic signal14 ₀ is centered on a center frequency 12 ₀, of a value CF₀. Basicsignal copies 14 ⁻², 14 ⁻¹, 14 ₊₁ and 14 ₊₂ are centered on centerfrequencies 12 ⁻², 12 ⁻¹, 12 ₊₁ and 12 ₊₂ of values CF⁻², CF⁻¹, CF₊₁ andCF₊₂. In theory, signal 10 can extend from zero frequency to infinity.In practice, such signals are truncated by a truncating bandwidthfilter.

Basic signal 14 ₀ exhibits a bandwidth BW₀, extending from a frequencyF₃ to a frequency F₄, which is typically the bandwidth of the discreteBaseband signal. Basic signal copies 14 ⁻², 14 ⁻¹, 14 ₊₁ and 14 ₊₂ eachexhibit bandwidths BW⁻² (between frequencies F₁ and F₂), BW⁻¹ (betweenfrequencies F₂ and F₃), BW₊₁ (between frequencies F₄ and F₅) and BW₊₂(between frequencies F₅ and F₆), respectively. It is noted that thevalue of each bandwidths BW⁻², BW⁻¹, BW₊₁ and BW₊₂ is equal to that ofbandwidth BW₀.

Demodulating the basic signal 14 ₀ with respect to center frequency 12 ₀(CF₀), shall reconstruct the modulating discrete Baseband signal.Similarly, demodulating any of the basic signal copies 14 _(—2), 14 ⁻¹,14 ₊₁ and 14 ₊₂ with respect to their respective center frequencies 12_(—2) (CF⁻²), 12 _(—1) (CF⁻¹), 12 ₊₁ (CF₊₁) and 12 ₊₂ (CF₊₂), shall alsoreconstruct modulating discrete Baseband signal.

Demodulation of the transmission signal can be performed in a jointfashion, for all basic signal copies. Joint demodulation is performedwith respect to center frequency 12 ₀, by sampling the transmissionsignal, prior to demodulation, thereby centering all basic signalcopies, on center frequency 12 ₀. Such joint demodulation can be used toincrease robustness, by allowing the Baseband signal to be recreated,from one, or more, basic signal copies.

It will be appreciated by those skilled in the art, that a Basebandsignal may be shaped, so as to exhibit a different spectral shape, byapplying various techniques which are well known in the art, the mostcommon being mixing the Baseband signal, using a mixer.

The disclosed technique makes use of this phenomenon to provide backwardcompatibility between different generations of communication standardsand methods. According to the disclosed technique, a new generationtransmitter incorporates a single carrier signal, for transmitting toboth old generation units and new generation units.

When transmitting to an old generation unit, the carrier signal ismodulated by a Baseband signal, according to an old generation Basebandbandwidth. The Baseband signal used for modulating the carrier signal,is shaped so as to produce, after duplication in the frequency domain,at least one copy. The old generation basic signal copies are produced,by a combination of portions of the duplicated basic signal copies,created from the shaped Baseband signal. Prior to modulation, the shapedBaseband signal is up-sampled, in order to duplicate the signal in thefrequency domain, according to principles illustrated above.

It will be appreciated, that digital mixing of the Baseband signal canbe implemented by multiplying the digital signal samples by a factor,which induces a phase change in the signal. In the disclosed technique,each sample of the digital Baseband data, is multiplied by a factorequal to

${\exp\left( {{j2\pi}\; k\frac{\Delta\; f}{f_{b}}} \right)},$where k is the sample index, Δf is the difference between the oldgeneration and new generation carrier frequencies, and f₁, is the oldgeneration Baseband bandwidth. It is noted, that by performing such amultiplication, the mixed (multiplied) Baseband signal, when duplicatedby up-sampling, will resemble copies of an old generation Basebandsignal, with respect to an old generation carrier frequency. Thus, anold generation device will be able to demodulate the mixed Basebandsignal, with respect to an old generation carrier frequency.

When transmitting to a new generation unit, the carrier signal ismodulated by a different Baseband signal, which may have a higher orlower, Baseband sampling rate, than that of the old generation.

Reference is now made to FIG. 1B, which is a schematic illustration, inthe frequency domain, of an original signal, generally referenced 20,and a shaped signal, generally referenced 30, which is produced byshaping the original signal 20, according to the principles illustratedabove.

Original signal 20 includes a basic signal 24, centered on frequencyCF₁, generally referenced 22, and having a bandwidth of BW₁. Shapedsignal 30 includes a basic signal 34, having a bandwidth of BW₁. It isnoted that basic signal 34, has a different spectral shape than that ofbasic signal 24 of shaped signal 20. According to the principlesillustrated above, shaped signal 30 is produced by shaping originalsignal 20, to the desired spectral shape of basic signal 34.

In general, mixing a signal function with a single frequency function isequivalent in the frequency domain to a convolution of the signalfunction with a delta function at that specific frequency. When themixer is analog, then the result shall be a linear shift of the signalfunction by an interval of the single frequency. Hence, if the signalfunction is centered on zero and includes frequencies in the range[−F_(Sa),F_(Sa)] and the specific frequency is F_(C), then the resultshall be a shifted representation of the signal function to center onF_(C), in the range [−F_(Sa)+F_(C),F_(Sa)+F_(C)].

When the mixer is digital, then the result shall be a cyclic shift ofthe signal function by an interval of the single frequency. Hence, ifthe signal function is centered on zero and includes frequencies in therange [−F_(Sd),F_(Sd)] and the specific frequency is F_(C) (wherein−F_(Sd)<F_(C)<F_(Sd)), then the result shall be a shifted representationof the signal function to center on F_(C), but in the range[−F_(Sd),F_(Sd)], wherein portions which are shifted beyond F_(Sd) are“pushed” back from the end of −F_(Sd). In the example set forth in FIG.1B, signal 34 is obtained from basic signal 24 by a cyclic shift. As aresult, frequencies F1 and F2 are moved to a new location, slightlyabove CF1.

Reference is now made to FIG. 2, which is a schematic illustration, inthe frequency domain, of three transmission signals, generallyreferenced 100, 110 and 120. Transmission signals 110 and 120 aredefined and produced in accordance with an embodiment of the disclosedtechnique. Transmission signals 100, 110 and 120 are produced bymodulating discrete Baseband signals onto carrier signals.

Transmission signal 100 includes a basic signal 104, which is centeredon a center frequency 102 (CF₁) and exhibits a bandwidth BW₁ extendingbetween frequencies F₂ and F₃. Transmission signal 100 is produced by anold generation transducer (not shown) and is intended for any unit whichis compatible therewith (i.e., typically, old generation units and newergeneration units which are compatible with the old generation).

Transmission signal 120 includes a basic signal 124, which is centeredon a center frequency 112 (CF₂) and exhibits a bandwidth BW₂ extendingbetween frequencies F₁ and F₆. Transmission signal 120 is produced by anew generation transducer (not shown) and is intended to any unit whichis compatible therewith (i.e., typically, new generation units).

Transmission signal 110 includes a basic signal 114 ₀, which is centeredon center frequency 112 (CF₂) of transmission signal 120, and exhibits abandwidth BW₁, extending between frequencies F₄ and F₅. Transmissionsignal 110 further includes basic signal copies 114 ⁻², 114 ⁻¹, 114 ₊₁and 114 ₊₂. It is noted that basic signal copy 114 ⁻¹, extends fromfrequency F₉ to frequency F₄, wherein F₄−F₉=BW₁. Basic signal 114 ₀, isshaped as so that when duplicated, basic signals copies 114 ₂ and 114 ₁,combine to include a copy of basic signal 104, centered on centerfrequency 102, exhibiting a bandwidth BW₁ extending between frequenciesF₂ and F₃. Accordingly, when received by an old generation unit, theportion of basic signal copy 114 ⁻², extending from frequency F₂ tofrequency F₉ and the portion of basic signal copy 114 ⁻¹, extending fromfrequency F₉ to frequency F₃, shall be perceived as an old generationtransmission. That old generation unit can demodulate the combinedportions of basic signal copies 114 _(—2) and 114 _(—1), betweenfrequencies F₂ and F₃, with respect to center frequency 102 (CF₁) inorder to receive data, according to the old generation Baseband samplingrate.

Accordingly, a new generation unit can produce transmission signal 110and transmit it to any unit which is compatible with the old generation(i.e., typically, old generation units and newer generation units whichare compatible with the old generation).

According to the disclosed technique, a signal shape is selected, so asto recreate the original Baseband signal, centered on a center frequencylocated an integer multiple of old generation Baseband bandwidths, awayfrom an old generation carrier frequency. A Baseband signal, shapedaccording to such a signal shape and up-sampled and modulated on a newgeneration carrier frequency, includes a copy which can be demodulatedaccording to an old generation Baseband bandwidth.

In the example set forth in FIG. 2, the original Baseband signal isshaped to be spectrally similar to basic signal 114 ₀, to allow fordemodulation of the duplicated copies, on center frequency 102 (CF₁).

According to one aspect of the disclosed technique, the new generationcarrier signal center frequency can be located higher than that of theold generation carrier frequency, as described in the example set forthin FIG. 2, or lower than the old generation carrier frequency. Accordingto another aspect of the disclosed technique, the frequency range of thenew generation transmission signal can extend beyond the frequency rangeof the old generation transmission signal. Both of these aspects shallbe described herein below, in FIG. 3.

Reference is now made to FIG. 3, which is a schematic illustration, inthe frequency domain, of three transmission signals, generallyreferenced 130, 140 and 150. Transmission signals 140 and 150 aredefined and produced in accordance with an embodiment of the disclosedtechnique. Transmission signals 130, 140 and 150 are produced bymodulating discrete Baseband signals onto continuous carrier signals.

Transmission signal 130 includes a basic signal 134, which is centeredon a center frequency 132 (CF₁) and exhibits a bandwidth BW₁ extendingbetween frequencies F₄ and F₅. Transmission signal 130 is produced by anold generation transducer (not shown) and is intended for any unit whichis compatible therewith (i.e., typically, old generation units and newergeneration units which are compatible with the old generation).

Transmission signal 150 includes a basic signal 154, which is centeredon a center frequency 142 (CF₂) and exhibits a bandwidth BW₂, extendingbetween frequencies F₁ and F₆. Transmission signal 150 is produced by anew generation transducer (not shown) and is intended for any unit whichis compatible therewith (i.e., typically, new generation units).

Transmission signal 140 includes a basic signal 144 ₀, which is centeredon center frequency 142 (CF₃) of transmission signal 150, and exhibits abandwidth BW₁, extending between frequencies F₇ and F₈. Transmissionsignal 140 further includes basic signal copies 144 ⁻⁴, 144 ⁻³, 144 ⁻²,144 ⁻¹, 144 ₊₁, 144 ₊₂, 144 ₊₃ and 144 ₊₄. It is noted that basic signalcopies 144 ⁻⁴ and 144 ₊₄ are partial copies of basic signal 144 ₀, astransmission signal 140 is limited by the same bandwidth filter whichlimits signal 150. It is further noted that basic signal 114 ₀ isproduced by shaping a sampled Baseband signal, in accordance with theprinciples illustrated above, and using the shaped signal to modulate acarrier signal. The portion of basic signal copy 144 ₊₂, extending fromfrequency F₄ to frequency CF₁, together with the portion of basic signalcopy 144 ₊₃, extending from frequency CF₁ to frequency F₅, form a signalwhich is similar to basic signal 134 of old generation unit, beingcentered on center frequency 132 and exhibiting a bandwidth of BW₁extending between frequencies F₄ and F₅. Accordingly, when received byan old generation unit, basic signal copies 144 ₊₂ and 144 ₊₃ may bedemodulated as an old generation transmission, with respect to centerfrequency 132 (CF₁) in order to retrieve the original Baseband signal,according to the old generation Baseband bandwidth.

Accordingly, a new generation unit can produce transmission signal 140and transmit it to any unit which is compatible with the old generation(i.e., typically, old generation units and newer generation units whichare compatible with the old generation).

The disclosed technique is applicable for wired communications as wellas wireless communications. The example which is described in FIG. 4herein below, addresses a wired communication standard known as HomePhoneline Networking Alliance ver. 2, which is also called HPNA-2. Thisexample shall present general requirements from a future new generationstandard, which shall be here referred to as HPNA-X.

Reference is now made to FIG. 4, which is a schematic illustration, inthe frequency domain, of three transmission signals, generallyreferenced 160, 170 and 180. Transmission signals 170 and 180 aredefined and produced in accordance with a further embodiment of thedisclosed technique. Transmission signals 160, 170 and 180 are producedby modulating discrete Baseband signals onto carrier signals.

Transmission signal 160 is produced according to HPNA-2 communicationstandard. Transmission signal 180 is produced according to HPNA-Xcommunication standard. Transmission signal 170 is produced according toHPNA-X communication standard but is intended to be received by HPNA-2communication standard compatible units.

HPNA-2 communication standard defines a transmission signal which iscentered on a carrier signal center frequency of 7 MHz, HPNA-2communication standard further defines an overall bandwidth of 6 MHz,extending from 4 MHz to 10 MHz.

HPNA-2 communication standards include several modes of operation forproducing a transmission signal with that carrier signal centerfrequency of 7 MHz. According to one HPNA-2 mode of operation, a 2 MHzbandwidth Baseband signal modulates the carrier signal center frequencyof 7 MHz. According to this mode of operation, the produced transmissionsignal includes three instances of a basic signal. With reference toFIG. 4, HPNA-2 transmission signal 160 includes a basic signal 164 ₀ andtwo basic signal copies 164 ⁻¹ and 164 ₊₁.

Basic signal 164 ₀ is centered on a center frequency 162 (7 MHz) andexhibits a bandwidth of 2 MHz, extending between 6 MHz and 8 MHz. Basicsignal copy 164 ⁻¹ is centered on 5 MHz and exhibits a bandwidth of 2MHz, extending between 4 MHz and 6 MHz. Basic signal copy 164 ₊₁ iscentered to 9 MHz and exhibits a bandwidth of 2 MHz, extending between 8MHz and 10 MHz. The HPNA-2 communication standard defines the two basicsignal copies 164 ⁻¹ and 164 ₊₁ for purposes such as improvedrobustness, and the like. Transmission signal 160 is produced by anHPNA-2 transducer (not shown) and is intended for any unit which iscompatible with the HPNA-2 communication standard.

According to the example of disclosed technique set forth in FIG. 4, apossible future HPNA-X communication standard defines a transmissionsignal which is centered on a carrier signal center frequency of 10 MHz,and having an overall frequency range of 10.5 MHz, extending from 4.75Mz to 15.25 Mz. It is noted that the overall frequency range, withrespect to the selected carrier signal center frequency, can be set tobe broader than 10.5 MHz or as mimimal as 4 MHz. Transmission signals170 and 180 are both centered on a single center frequency 172 (10 MHz).

Transmission signal 180 includes a basic signal 184, which is centeredon center frequency 172 (10 MHz) and exploits the entirety of thebandwidth of 10.5 MHz. HPNA-X transducer (not shown) producestransmission signal 180 by modulating the 10 MHz carrier signal with a10 MHz sampled Baseband signal. Transmission signal 180 is produced bythat HPNA-X transducer and is intended for any unit which is compatiblewith HPNA-X communication standard.

Transmission signal 170 includes a basic signal 174 ₀, which is centeredto center frequency 172 (10 MHz) of transmission signal 180, andexhibits a bandwidth of 2 MHz, extending between 9 MHz and 11 MHz. It isnoted that basic signal 174 ₀, is produced by modulating the carrierfrequency 172, with a shaped sampled Baseband signal, in accordance withthe principles illustrated above. Transmission signal 170 furtherincludes basic signal copies 174 ⁻², 174 ⁻¹, 174 ₊₁ and 174 ₊₂ and twopartial basic signal copies 174 ⁻³ and 174 ₊₃.

Basic signal copy 174 ⁻² is centered on a center frequency of 6 MHz andexhibits a bandwidth of 2 MHz, extending between 5 MHz and 7 MHz. Basicsignal copy 174 ⁻¹ is centered on a center frequency of 8 MHz andexhibits a bandwidth of 2 MHz, extending between 7 MHz and 9 MHz.Accordingly, the combination of the portion of basic signal copy 174 ⁻²,extending from 6 MHz to 7 MHz, and the portion of basic signal copy 174⁻¹, extending from 7 MHz to 8 MHz, form a signal which is compatiblewith basic signal copy 1640 of transmission signal 160. Furtheraccordingly, the combination of the portion of basic signal copy 174 ⁻¹,extending from 8 MHz to 9 MHz, and the portion of basic signal copy 174₀, extending from 9 MHz to 10 MHz, form a signal which is compatiblewith basic signal 164 ₊₁ of transmission signal 160.

Partial basic signal copy 174 ⁻³ extends between 4.75 MHz and 5 MHz andis a portion of a basic signal copy (not shown) which is centered on acenter frequency of 4 MHz and exhibits a bandwidth of 2 MHz. Partialbasic signal copy 174 ₊₃ extends between 15 MHz and 15.25 MHz and is aportion of a basic signal copy (not shown) which is centered on a centerfrequency of 16 MHz and exhibits a bandwidth of 2 MHz.

Together, basic signal copies 174 ⁻², 174 ⁻¹ and 174 ₀ and partial basicsignal copy 174 ⁻³ form a signal which is can be demodulated bycommunication devices compatible with the requirements of the HPNA-2communication standard. Accordingly, when received by an HPNA-2 unit,basic signal copies 174 ⁻², 174 ⁻¹ and 174 ₀ and the partial basicsignal copy 174 ⁻³ shall be perceived as an HPNA-2 transmission. Hence,an HPNA-2 unit can demodulate the transmission signal by using basicsignal copies 174 ⁻², 174 ⁻¹ and the portion of basic signal copy 174 ₀extending from 9 MHz to 10 MHz, in order to reconstruct the originalBaseband signal, according to the HPNA-2 baud rate.

It is noted that both transmission signals 180 and 170 are produced bythe same HPNA-X unit using the same carrier signal center frequency 172of 10 MHz. It is further noted that the disclosed technique can beapplied for other HPNA-2 modes of operation, in the same manner.

Reference is now made to FIG. 5, which is a schematic illustration of anetwork architecture, generally referenced 250, which includescommunication devices from different generations.

Network architecture 250 included a network 258, two old generationcommunication devices 262 and 264 and three new generation communicationdevices 252, 254 and 256. Old generation communication devices 262 and264 are operative to produce and transmit messages according to an oldcommunication standard (OCS) and are further operative to receive anddecipher such messages. New generation communication devices 252, 254and 256 are operative to produce and transmit messages according to anew communication standard (NCS) and are further operative to receiveand decipher such messages. New generation communication devices 252,254 and 256 are further operative to produce and transmit messages,which are compatible with the old communication standard (OCS),according to the disclosed technique.

New generation communication devices 252, 254 and 256 are furtheroperative to produce and transmit messages, which are compatible withthe old communication standard (OCS), according to the disclosedtechnique.

Network architecture 250 is constructed according to a bus architecture.Hence, all of the communication devices 252, 254, 256, 262 and 264,which are coupled therewith, are operative to detect any signal which istransmitted over the network, provided that this signal is within theirrespective frequency range. However, it is noted that any architectureis applicable for the disclosed technique.

When new generation communication devices transmit new generation formatdata across the network, old generation communication devices, mustignore such data. In accordance with another embodiment of the disclosedtechnique, such new generation data is encapsulated in a transmission,which includes a fixed old-generation portion of a header That oldgeneration header portion, is shaped according to disclosed technique,so as to allow demodulation by old generation devices. The oldgeneration header portion includes instructions for old generationcommunication devices, to ignore the rest of the transmission. The newgeneration data, is produced in new generation format, and can thereforebe accessed, only by the new generation communication devices.

According to a further embodiment of the disclosed technique, an oldgeneration header portion, instructing old generation devices to ignorethe rest of the transmission, is shaped as to allow demodulation by oldgeneration devices, and permanently stored in the new generation devicememory. Since the header portion, which instructs old generation devicesto ignore the rest of the transmission, is identical for all datatransmissions the stored header portion may be attached to alltransmissions not intended for old generation devices. Attaching thestored header portion eliminates the need for on-line shaping of theheader portion, thus conserving real-time processing resources.

Reference is now made to FIG. 6A, which is a schematic illustration of atransmitter, generally referenced 270, of new generation device 252 ofFIG. 5, constructed and operative in accordance with another embodimentof the disclosed technique. Transmitter 270 includes a high baud ratesignal generator 272, a low baud rate signal generator 276, a switch278, a controller 274, a modulator 282, a carrier signal generator 280,a communication interface 284, a signal shaper 286, and an up-sampler288.

High baud rate signal generator 272 and up-sampler 288 are alternatelycoupled with switch 278. Signal shaper 286 is coupled with low baud ratesignal generator 276 and with up-sampler 288. Switch 278 is furthercoupled with controller 274 and to modulator 282. Modulator 282 isfurther coupled with carrier signal generator 280 and to communicationinterface 284. Communication interface 284 is further coupled withnetwork 258 (not shown) of FIG. 5. Transmitter 270 is operative toproduce transmission signals compatible with both old generation formatdevices and new generation format devices, by employing the aboveillustrated technique.

When transmitting to new generation format devices, transmitter 270 useshigh baud rate signal generator 272, to generate Baseband data. Highbaud rate signal generator 272 provides the Baseband data to modulator282, via switch 278. Carrier signal generator 280 produces a carriersignal and provides it to modulator 282. Modulator 282 modulates thehigh rate Baseband signal with the carrier signal, thereby producingtransmission signal. Modulator 282 provides the transmission signal tocommunication interface 284, which in turn, transmits the transmissionsignal to network 258.

When transmitting to old generation format devices, transmitter 270 useslow baud rate signal generator 276, to generate Baseband data. Low baudrate signal generator 276 provides the Baseband data to signal shaper286, which shapes the Baseband data so as to produce an old generationbasic signal copy, when duplicated in the frequency domain, and used tomodulate the new generation carrier signal, according to the techniqueillustrated herein above. Signal shaper 286 provides the shaped Basebanddata to up-sampler 288. Up-sampler 288 performs up-sampling of the data,to produce a Baseband signal, which includes multiple copies, of theshaped Baseband signal, in accordance with the technique illustratedabove. Up-sampler 288 provides the up-sampled Baseband signal tomodulator 282, via switch 278. Other elements of the transmission pathare unchanged with respect to transmission to new generation formatdevices.

According to the example set forth in FIG. 2, when transmitting to newgeneration format devices, high baud rate signal generator 272 providesBaseband data having a bandwidth of BW₂, to transmitter 270. Modulator282 modulates this Baseband data with carrier signal from carrier signalgenerator 280, having a frequency 112, to produce transmission signal120. When transmitting to old generation format devices, low baud ratesignal generator 276 provides Baseband data, using, having a bandwidthof BW₁, to transmitter 270. Signal shaper 286 shapes the sampledBaseband data to produce a shaped Baseband signal, spectrally similar tobasic signal copy 1140. Up-sampler 288, up-samples the Baseband data, toproduce multiple Baseband signal copies 114 ⁻², 114 ⁻¹, 114 ⁻⁰, 114 ₊₁,and 114 ₊₂. Modulator 282 modulates up-sampled Baseband data withcarrier signal from carrier signal generator 280, having a frequency112, to produce transmission signal 110, which includes basic signal 114₀ and basic signal copies 114 ⁻², 114 ⁻¹, 114 ₊₁ and 114 ₊₂.

According to the example set forth in FIG. 4, when transmitting to newgeneration format devices, high baud rate signal generator 272 providesBaseband data, using, having a bandwidth of 10 MHz, to transmitter 270.Modulator 282 modulates sampled Baseband data with carrier signal fromcarrier signal generator 280, having a frequency of 10 MHz, to producetransmission signal 180. When transmitting to old generation formatdevices, low baud rate signal generator 276 provides Baseband datahaving a bandwidth of 2 MHz, to transmitter 270. Signal shaper 286shaped the sampled Baseband data to produce a shaped Baseband signal,spectrally similar to basic signal copy 1740. Up-sampler 288 up-samplesBaseband signal, to produce multiple basic signal copies 174 ⁻¹ to 174₊₁, of Baseband signal. Modulator 282 modulates up-sampled Baseband datawith carrier signal from carrier signal generator 280, having afrequency of 10 MHz, to produce a transmission signal 170, whichincludes basic signal 174 ₀ and basic signal copies 174 ⁻², 174 ⁻¹, 174₊₁ and 174 ₊₂.

Controller 274 performs selection between different generation formatdata, by operating switch 278, to couple with desired signal generator.Controller 274 is controlled by other elements (not shown) ofcommunication device 252 (FIG. 5).

Alternatively, the low sampling rate signal generator, and the highsampling rate signal generator, may be combined in a single signalgenerator element, which operates according to two different modes. Insuch an embodiment, both sampling rates are provided by reducing thesampling rate of a signal generator to the sampling rate required byeach mode. Such a combined signal generator element is coupled to themixer. The mixer is further coupled to a controller, which operates themixer, to shape Baseband data, when transmitting to old generationdevices. Other aspects of the transmitter remain essentially the same asdescribed for the transmitter in FIG. 6A. According to anotherembodiment of the disclosed technique (not shown), which is directed foroperating in digital mode, the signal shaper 286 and up-sampler 288 arecoupled after modulator 282, and operate on carrier modulated signals.

Reference is now made to FIG. 6B, which is a schematic illustration of atransmitter, generally referenced 2970, of new generation device 252 ofFIG. 5, constructed and operative in accordance with another embodimentof the disclosed technique. Transmitter 290 includes a high baud ratesignal generator 292, a modulator 294, a carrier signal generator 296, asignal shaper 298, a low baud rate signal generator 300, an up-sampler302, a controller 304, a band pass filter 306, a switch 308, and acommunication interface 310.

High baud rate signal generator 292 is coupled with modulator 294.Modulator 294 is further coupled with carrier signal generator 296 andwith switch 308. Signal shaper 298 is coupled with carrier signalgenerator 296, low baud rate signal generator 300, and with up-sampler302. Band pass filter 306 is coupled with up-sampler 302, and withswitch 308. Switch 308 is further coupled with controller 304, and withcommunication interface 310. Communication interface 310 is furthercoupled with network 258 (not shown) of FIG. 5. Transmitter 290 isoperative to produce transmission signals compatible with both oldgeneration format devices and new generation format devices, byemploying the above illustrated technique.

When transmitting to new generation format devices, transmitter 290 useshigh baud rate signal generator 292, to generate Baseband data. Highbaud rate signal generator 292 provides the Baseband data to modulator294. Carrier signal generator 296 produces a carrier signal and providesit to modulator 294. Modulator 294 modulates the high rate Basebandsignal with the carrier signal, thereby producing transmission signal.Modulator 294 provides the transmission signal to switch 308, which inturn, provides the transmission signal to communication interface 310,which transmits the transmission signal to network 258.

When transmitting to old generation format devices, transmitter 290 useslow baud rate signal generator 300, to generate Baseband data. Low baudrate signal generator 300 provides the Baseband data to signalshaper298, which shapes the Baseband data so as to produce an oldgeneration basic signal copy, when duplicated in the frequency domain,and used to modulate the new generation carrier signal, according to thetechnique illustrated herein above. Signal shaper 298 further mixed theshaped Baseband signal with a carrier signal, received from carriersignal generator 296, to produce a mixed Baseband signal. Signal shaper298 provides the mixed Baseband data to up-sampler 302. Up-sampler 302performs up-sampling of the data, to produce a Baseband signal, whichincludes multiple copies, of the shaped Baseband signal, in accordancewith the technique illustrated above. Up-sampler 302 provides theup-sampled Baseband signal to band pass filter 306, which restricts theup-sampled signal to the new generation signal bandwidth. Thecombination of the mixing performed by signal shaper 298 an thefiltering performed by band pass filter 306, effectively modulates theshaped Baseband signal on a new generation carrier signal thus producinga transmission signal. Band pass filter 306, provides the transmissionsignal to communication interface 310, via switch 308. Other elements ofthe transmission path are unchanged with respect to transmission to newgeneration format devices.

Controller 304 performs selection between different generation formatdata, by operating switch 310, to couple with desired transmissionsignal source. Controller 310 is controlled by other elements (notshown) of communication device 252 (FIG. 5).

Reference is now made to FIG. 7A, which is a schematic illustration of atransmitter, generally referenced 330, of new generation device 252 ofFIG. 5 constructed and operative in accordance with another embodimentof the disclosed technique.

Transmitter 330 includes a high baud rate signal generator 332, a memoryelement 334, a switch 336, a carrier signal generator 338, a modulator340, a controller 344, and a communication interface 342. Switch 336 iscoupled with high baud rate signal generator 332, with memory element334, with controller 344 and with modulator 340. Modulator 340 isfurther coupled with carrier signal generator 338 and with communicationinterface 342. Communication interface 342 is coupled with network 258of FIG. 5 (not shown). Transmitter 330 is operative to producetransmission signals compatible with new generation format devices,which will be ignored by old generation format devices, thus allowingold, and new, generation devices to coexist on the same physicalnetwork, without interference.

Transmitter 330 uses high baud rate signal generator 332, to generateBaseband data. High baud rate signal generator 332 provides the Basebanddata to switch 336. Memory element 334 provides pre-stored oldgeneration format header portion, to switch 336. The old generationformat header portion instructs old generation devices to ignore therest of the transmission. The stored old generation format headerportion, is spectrally shaped, as to resemble old generation formatheader portion, when demodulated with respect to old generation carriersignal, in accordance with the principles illustrated herein above.Controller 344 operates switch 336 to prepend old generation formatheader portion, to Baseband data, creating a pre-modulated transmissionsignal. Switch 336 provides pre-modulated transmission signal tomodulator 340. Carrier signal generator 338 produces a carrier signaland provides it to modulator 340. Modulator 34 ₀ modulates thepre-modulated transmission signal with the carrier signal, therebyproducing transmission signal. Modulator 340 provides the transmissionsignal to communication interface 342, which in turn, transmits thetransmission signal to network 258.

In accordance with this embodiment of the disclosed technique, oldgeneration devices will therefore ignore all transmissions from the newgeneration device, allowing coexistence of old, and new generationdevices, on the same physical network.

Reference is now made to FIG. 7B, which is a schematic illustration of atransmitter, generally referenced 350, of new generation device 252 ofFIG. 5 constructed and operative in accordance with another embodimentof the disclosed technique. Transmitter 350 includes a high baud ratesignal generator 352, a memory element 358, a switch 360, a carriersignal generator 354, a modulator 356, a controller 364 and acommunication interface 362.

Modulator 356 is coupled with high baud rate signal generator 352,carrier signal generator 354, and with switch 360. Switch 360 is furthercoupled with memory element 358, with controller 364 and withcommunication interface 362. Communication interface 362 is coupled withnetwork 258 of FIG. 5 (not shown). Transmitter 350 is operative toproduce transmission signals compatible with new generation formatdevices, which will be ignored by old generation format devices, thusallowing old, and new, generation devices to coexist on the samephysical network, without interference.

Transmitter 350 uses high baud rate signal generator 352, to generateBaseband data. High baud rate signal generator 352 provides the Basebanddata to modulator 356. Modulator 356 modulated the Baseband data with acarrier signal received from carrier signal generator 354. Memoryelement 358 provides pre-stored old generation format header portion,already modulated with a new generation carrier signal, having the samefrequency as the signal provided by carrier signal generator 354, toswitch 360. The old generation format header portion instructs oldgeneration devices to ignore the rest of the transmission. The storedold generation format header portion, is spectrally shaped, as toresemble old generation format header portion, when demodulated withrespect to old generation carrier signal, in accordance with theprinciples illustrated herein above. Controller 364 operates switch 360to prepend old generation format header portion, to the modulatedBaseband data, received from modulator 356, creating a transmissionsignal. Switch 360 provides the transmission signal to communicationinterface 362, which in turn, transmits the transmission signal tonetwork 258.

In accordance with this embodiment of the disclosed technique, oldgeneration devices will therefore ignore all transmissions from the newgeneration device, allowing coexistence of old, and new generationdevices, on the same physical network.

Reference is now made to FIG. 8, which is a schematic illustration of amethod for backward compatible communication, operative in accordancewith another embodiment of the disclosed technique.

In procedure 400, a carrier frequency for a new generation device isselected. It is noted that no constrains exist regarding the newgeneration carrier frequency.

In procedure 402, the frequency range for the new generation device isselected. The frequency range is selected so as to overlap at least oneinstance, of the old generation basic signals.

In the example set forth in FIG. 4, the selected frequency range,between 4.75 MHz and 15.25 MHz, overlaps two instances of the oldgeneration basic signal, 164 ₀ and 164 ₊₁. It is noted that the selectedfrequency range, could also have been selected to overlap one, or threeof the basic signal instances, for example, by selecting a frequencyrange of 8 MHz-12 MHz, which overlaps only one instance of the basicsignals (referenced 164 ₊₁).

In procedure 404, a signal shape for the Baseband signal is selected,for use when transmitting to old generation devices. The signal shape isselected so as to recreate an old generation basic signal copy, whenduplicated in the frequency domain, and further modulates the newgeneration carrier signal. In the example set forth in FIG. 4, theselected signal shape, modifies the original signal to a shaped signal,so that a combination of portions of adjacent copies thereof, areperceived to be centered on a frequency located at an integer multipleof old generation Baseband bandwidths, away from an old generationcarrier frequency.

Procedure 406 is directed for transmitting to old generation devices. Inprocedure 406, data sampled with the old generation sampling ratebandwidth is shaped in accordance with the shape selected in procedure404. The shaped sampled data modulates the new generation carriersignal, thereby producing a transmission signal which includes at leastone instance of a basic signal according to the old generation format,in accordance with the principles illustrated above.

In the example set forth in FIG. 4, 2 MHz shaped sampled data, is usedto modulate the 10 MHz carrier signal. The resulting transmission signalincludes instances of basic signal 174 ⁻², 174 ⁻¹, 174 ₀, 174 ₊₁, and174 ₊₂, when duplicated in the frequency domain, in accordance with theprinciples illustrated above. Basic signal copies 174 ⁻¹, 174 ₀ and aportion of basic signal copy 174 ⁻², produce signals which arecompatible with old generation basic signals 164 ₀ and 164 ₊₁, thusallowing old generation devices to demodulate the transmitted signal andextract the data.

Procedure 408 is directed for transmitting to new generation devices. Inprocedure 408, data sampled with the new generation sampling ratebandwidth is prepended with a header portion generated in the old formatdata and shaped in accordance with the shape selected in procedure 404.The header portion instructs old generation format devices, to ignorethe rest of the transmission. The combined data and header portion,modulate the new generation carrier signal, thereby producing atransmission signal which includes a single instance of a basic signalaccording to the new generation format, and a header portion whichensures that old generation format devices will ignore the transmission.

It will be appreciated by persons skilled in the art that the presentinvention is not limited to what has been particularly shown anddescribed hereinabove. Rather the scope of the present invention isdefined only by the claims, which follow.

1. A multiple generation communications device comprising: a signalgenerator, generating a second generation bandwidth Baseband signal; amemory element; a controller; a switch, coupled with said controller,said signal generator and said memory element; a carrier signalgenerator, providing a second generation carrier signal; a modulator,coupled with said switch and said carrier signal generator, wherein saidmemory element contains a shaped copy of a first generation formatBaseband signal, shaped so as to recreate said first generation formatBaseband signal when modulated with said second generation carriersignal and demodulated with respect to a first generation carriersignal.
 2. The multiple generation communications device, according toclaim 1, wherein said shaped copy of a first generation format Basebandsignal, is at least a portion of a first generation format headerinstructing first generation devices to ignore any remaining transmitteddata.
 3. The multiple generation communications device, according toclaim 2, wherein said shaped copy of a first generation format Basebandsignal, is a predetermined first generation format signal intended forfirst generation devices.
 4. The multiple generation communicationsdevice, according to claim 2, wherein said switch prepends said at leasta portion of a first generation format header to said second generationbandwidth Baseband signal, thereby producing a pre-modulated secondgeneration transmission signal when transmitting to second generationdevices, in the presence of said first generation devices.
 5. Themultiple generation communications device, according to claim 3, whereinsaid switch provides said shaped copy of a first generation formatBaseband signal, producing a pre-modulated first generation transmissionsignal, when transmitting said predetermined first generation formatsignal to said first generation devices.
 6. The multiple generationcommunications device, according to claim 4, wherein said modulatormodulates said pre-modulated second generation transmission signal, withsaid second generation carrier signal, thereby producing a transmissionsignal.
 7. The multiple generation communications device, according toclaim 5, wherein said modulator modulates said pre-modulated firstgeneration transmission signal, with said second generation carriersignal, thereby producing a transmission signal.
 8. The multiplegeneration communications device, according to claim 1, furthercomprising a communication interface, coupled with said modulator, saidcommunication interface providing said transmission signal to a network.9. The multiple generation communications device according to claim 1,wherein said second generation bandwidth Baseband signal is in digitalformat.
 10. The multiple generation communications device according toclaim 1, wherein said second generation bandwidth Baseband signal is inanalog format.
 11. The multiple generation communications deviceaccording to claim 1, wherein said shaped copy of a first generationformat signal is in digital format.
 12. The multiple generationcommunications device according to claim 1, wherein said shaped copy ofa first generation format signal is in analog format.
 13. The multiplegeneration communications device according to claim 1, wherein saidsecond generation carrier signal is in digital format.
 14. The multiplegeneration communications device according to claim 1, wherein saidsecond generation carrier signal is in analog format.
 15. The multiplegeneration communications device according to claim 1, wherein saidcommunication interface is further coupled with a wired network.
 16. Themultiple generation communications device according to claim 1, whereinsaid communication interface is further coupled with a wireless network.17. A multiple generation communications network architecturecomprising: a network; at least one first generation communicationsdevice, coupled with said network; and at least one second generationcommunications device, coupled with said network, wherein at least oneof said at least one second generation communications device comprises:a signal generator, generating a second generation bandwidth Basebandsignal; a memory element; a switch, coupled with said controller, saidfirst signal generator and said memory element; a carrier signalgenerator, providing a second generation carrier signal; a modulator,coupled with said switch and said carrier signal generator, wherein saidmemory element contains a shaped copy of a first generation formatBaseband signal, shaped so as to recreate said first generation formatBaseband signal when modulated with said second generation carriersignal and demodulated with respect to a first generation carriersignal.
 18. The multiple generation communications network according toclaim 17, wherein said network is a wired network.
 19. The multiplegeneration communications network according to claim 17, wherein saidnetwork is a wireless network.
 20. A multiple generation communicationsdevice comprising: means for generating a second generation bandwidthBaseband signal; means for storing; means for controlling; means forswitching, coupled with said means for controlling, said means forgenerating a second generation bandwidth Baseband signal and said meansfor storing; means for generating a carrier signal, providing a secondgeneration carrier signal; means for modulating, coupled with said meansfor switching and said means for generating a carrier signal, whereinsaid means for storing contains a shaped copy of a first generationformat Baseband signal, shaped so as to recreate said first generationformat Baseband signal when modulated with said second generationcarrier signal and demodulated with respect to a first generationcarrier signal.
 21. The multiple generation communications device,according to claim 20, wherein said shaped copy of a first generationformat Baseband signal, is at least a portion of a first generationformat header instructing first generation devices to ignore anyremaining transmitted data.
 22. The multiple generation communicationsdevice, according to claim 20, wherein said shaped copy of a firstgeneration format Baseband signal, is a predetermined first generationformat signal intended for first generation devices.
 23. The multiplegeneration communications device, according to claim 21, wherein saidmeans for switching prepends said at least a portion of a firstgeneration format header to said second generation bandwidth Basebandsignal, thereby producing a pre-modulated second generation transmissionsignal, when transmitting to second generation devices, in the presenceof said first generation devices.
 24. The multiple generationcommunications device, according to claim 22, wherein said means forswitching provides said shaped copy of a first generation formatBaseband signal, thereby producing a pre-modulated first generationtransmission signal, when transmitting said predetermined firstgeneration format signal to said first generation devices.
 25. Themultiple generation communications device, according to claim 23,wherein said means for modulating modulates said pre-modulated secondgeneration transmission signal, with said second generation carriersignal, thereby producing a transmission signal.
 26. The multiplegeneration communications device, according to claim 24, wherein saidmeans for modulating modulates said pre-modulated first generationtransmission signal, with said second generation carrier signal, therebyproducing a transmission signal.
 27. The multiple generationcommunications device, according to claim 20, further comprising a meansfor communicating with a network, coupled with said means formodulating, said means for communicating with a network providing saidtransmission signal to a network.